Currently undocumented: http://docs.python.org/py3k/c-api/gen.html
Public API in a released version of Python: http://hg.python.org/cpython/file/3.2/Include/genobject.h

Please correct me if I'm wrong, but I think PyGen_NeedsFinalizing should not be an API function because it is only used, nor _PyGen_FetchStopIterationValue. In the attached patch I've removed PyGen_NeedsFinalizing and _PyGen_FetchStopIterationValue fom the public API.

For the record, PyGen_NeedsFinalizing still exists but it isn't used anymore in the code base (following PEP-442).

What should be done for the PyGen_NeedsFinalizing API? Does it need to be documented or should it be removed since it's no longer used in the code base?

Thanks!

Cheryl: it may be useful to do a code search to find out whether any third-party projects are relying on PyGen_NeedsFinalizing.

Thanks Antoine.

Do you have a good way for searching third party projects? I searched on Github and I'm getting a lot of references to the CPython filenames. I don't know how to check if anyone is making calls to the function. But, maybe that's the point and it can't be removed if there's a chance that anyone uses it? Thanks!

This is what I tried on Github:
PyGen_NeedsFinalizing -filename:ceval -filename:genobject -filename:gcmodule

I think https://searchcode.com/ may have a larger indexing base than GitHub alone.

And, yes, you'll see many duplicates of the CPython source code... Visual inspection may be needed :-/

Thanks again, Antoine. I'll see what I can come up with. :-)

My searches show references to this function in CPython cloned repositories. From @pitrous's views, I think it is better to deprecate it with a removal notice for a later release.

I have deprecated the Function instead and will be removed in the next release in this PR #15702 .

PyGen_NeedsFinalizing() was added by:

commit 49fd7fa
Author: Thomas Wouters <thomas@python.org>
Date: Fri Apr 21 10:40:58 2006 +0000

Merge p3yk branch with the trunk up to revision 45595. This breaks a fair
number of tests, all because of the codecs/_multibytecodecs issue described
here (it's not a Py3K issue, just something Py3K discovers):
http://mail.python.org/pipermail/python-dev/2006-April/064051.html

Hye-Shik Chang promised to look for a fix, so no need to fix it here. The
tests that are expected to break are:

test_codecencodings_cn
test_codecencodings_hk
test_codecencodings_jp
test_codecencodings_kr
test_codecencodings_tw
test_codecs
test_multibytecodec

This merge fixes an actual test failure (test_weakref) in this branch,
though, so I believe merging is the right thing to do anyway.

It was used in this gcmodule.c function:

/* Return true if object has a finalization method.
 * CAUTION:  An instance of an old-style class has to be checked for a
 *__del__ method, and earlier versions of this used to call PyObject_HasAttr,
 * which in turn could call the class's __getattr__ hook (if any).  That
 * could invoke arbitrary Python code, mutating the object graph in arbitrary
 * ways, and that was the source of some excruciatingly subtle bugs.
 */
static int
has_finalizer(PyObject *op)
{
        if (PyInstance_Check(op)) {
                assert(delstr != NULL);
                return _PyInstance_Lookup(op, delstr) != NULL;
        }
        else if (PyType_HasFeature(op->ob_type, Py_TPFLAGS_HEAPTYPE))
                return op->ob_type->tp_del != NULL;
        else if (PyGen_CheckExact(op))
                return PyGen_NeedsFinalizing((PyGenObject *)op);
        else
                return 0;
}

(2) The PEP-442 implementation made PyGen_NeedsFinalizing() useless:

commit 796564c
Author: Antoine Pitrou <solipsis@pitrou.net>
Date: Tue Jul 30 19:59:21 2013 +0200

Issue bpo-18112: PEP-442 implementation (safe object finalization).

Replaced:

/* Return true if object has a finalization method. */
static int
has_finalizer(PyObject *op)
{
    if (PyGen_CheckExact(op))
        return PyGen_NeedsFinalizing((PyGenObject *)op);
    else
        return op->ob_type->tp_del != NULL;
}

with:

/* Return true if object has a pre-PEP 442 finalization method. */
static int
has_legacy_finalizer(PyObject *op)
{
    return op->ob_type->tp_del != NULL;
}

--

The last reference to PyGen_NeedsFinalizing() can be found in ceval.c:

    case TARGET(SETUP_FINALLY): {
        /* NOTE: If you add any new block-setup opcodes that
           are not try/except/finally handlers, you may need
           to update the PyGen_NeedsFinalizing() function.
           */

        PyFrame_BlockSetup(f, SETUP_FINALLY, INSTR_OFFSET() + oparg,
                           STACK_LEVEL());
        DISPATCH();
    }

The function is not documented nor tested.

I searched for usage of PyGen_NeedsFinalizing() in C code in GitHub:
https://github.com/search?l=C&p=1&q=PyGen_NeedsFinalizing&type=Code

I only found copies of the CPython code source: PyGen_NeedsFinalizing() definition in genobject.h.

IHMO we can safely remove the function right now. If someone complains, we can reintroduce it later. We just have to document clearly its removal at:
https://docs.python.org/dev/whatsnew/3.9.html#build-and-c-api-changes

New changeset 74b662c by Victor Stinner (Joannah Nanjekye) in branch 'master':
bpo-15088 : Remove PyGen_NeedsFinalizing() (GH-15702)
74b662c

I merged Joannah's change: thanks.

If anyone uses the removed function, please complain before Python 3.9.0 release :-)